The present invention relates to improved disposable articles such as diapers, incontinent products, disposable garments, feminine hygiene products, and the like, having a refastenable pressure-sensitive adhesive fastening tape tab system.
Disposable diapers or incontinence articles, and other disposable garments requiring liquid holdout, are typically made with a liquid impermeable layer. This liquid impermeable layer is generally the outermost layer in the disposable garment. In order to facilitate the wearability and conformability of the disposable garment and minimize costs the liquid impermeable layer typically is an extremely thin film, or laminate with a thin film layer, generally formed of a thermoplastic polymer such as a polyolefin like a polyethylene polymer, copolymer or blend. This same thin polymer film is also generally used as the adhesion surface to which a pressure-sensitive adhesive fastening tab is adhered in order to effect closure of the disposable diaper or other garment. Typically one end of the pressure-sensitive adhesive fastening tab is permanently adhered to one edge region of the garment on the polymer film with the second opposing end of the fastening tab preferably designed to removably attach to an outer surface of the garment adjacent to an opposing edge of the garment. This second or free end of the fastening tab would typically adhere to the thin thermoplastic film or film layer forming the liquid impermeable layer.
A problem with the above system is that in order to provide a secure permanent attachment at the fastening tab first end, the fastening tab pressure sensitive adhesive is sufficiently aggressive such that if the second free end of the fastening tab is removed from the disposable garment it causes the thin polymer film or film layer to tear. Various solutions have been proposed in the art to address this problem. For example, it has been proposed to increase the tensile strength of the diaper backsheet such as by increasing the thickness of the backsheet, using polymers that have higher tensile strengths, or some combination thereof; U.S. Pat. No. 5,147,346 (coextruded backsheet having a high modulus strengthening layer), European Patent No. 256 885 B1 (proposes a diaper backsheet comprising a resin blend of polypropylene and low density polyethylene having a thickness of from 1 to 1.5 mils., a thickness range greater than that for typical commercial backsheets, and a tensile strength of at least 550 grams), U.S. Pat. No. 5,084,039 (proposes a blend of polyethylene and an anti pop-off material, such as an ethylene propylene copolymer) and U.S. Pat. No. 4,880,422 (proposes a diaper backsheet formed from a blend of polypropylene and polyethylene to increase tape tab fastening adhesion and increase tensile strength). Although these stronger backsheets are less resistant to tearing, they are also stiffer and less conformable and significantly more costly than a typical thin diaper backsheet material.
It has also been proposed to decrease the fastening tape tab adhesive peel strength, by use of a less aggressive or less tacky pressure-sensitive adhesive. Although this may decrease the occurrence of tearing of the diaper backsheet, it also significantly increased the possibility that the tape tab could pop-off or fail during use. Generally, it was found difficult to match a pressure-sensitive adhesive to available thin diaper backsheets to provide the desired levels of adhesion performance under a variety of conditions, refastenability without tearing and backsheet conformability and cost.
As an alternative to strengthening the entire diaper backsheet there have been numerous proposals to strengthen just the portion of the backsheet which is adhered to the fastening tape tab. For example, U.S. Pat. No. 3,867,940 (Mesek) proposes reinforcing the diaper backsheet with a scrim or film attached to the inner or outer face of the diaper backsheet at those locations where the diaper fastening tape tab is adhered. This reinforcement is to prevent the backsheet from being torn or distorted while the diaper is being worn or adjusted by the parent (e.g., by removing and adjusting the location of the tape tab). A variation on this is proposed by Japanese Utility Model No. 74910 (1982), which proposes using a small pressure-sensitive adhesive tape attached only at the specific edge location of the diaper where the diaper fastening tape tab free end is most likely to be releasably attached.
Larger areas of reinforcement (as in Mesek), at only the location where the fastening tape tab free end is attached(as in the above Japanese Utility Model No. 74910) are proposed, for example, in U.S. Pat. No. 4,643,730, which proposes a radiation curable coating on an inner face of the diaper backsheet. Similarly, U.S. Pat. No. 4,296,710 proposes coating an inside surface of the diaper backsheet with a hot-melt adhesive to provide a large area of reinforcement. U.S. Pat. No. 4,210,144 likewise proposes reinforcing the inner face of the diaper backsheet with a coating, such as a hot-melt adhesive. European Patent No. 80647 B1 proposes gluing a thin plastic material on an outside face of the diaper backsheet, which is also taught in UK Patent No. 2,129,689 B, which proposes gluing one or more plastic strips to the outside front portion of the diaper, which plastic strips are preferably embossed to control the level of adhesion by the diaper fastening tape tab.
Japanese Patent Kokai No. 64-77604 and Utility Model No. Showa No. 64-37405 proposes coating the outside surface of a diaper backsheet with a heat-curable silicone release material and long chain alkyl release material, respectively, to enable the diaper fastening tape tabs to be adhered and reattached.
The invention addresses providing an improved system for releasably and repeatedly attaching a high tack conventional diaper fastening tape to thin films and the like such as used as a diaper backsheet.